where the individual self energy terms in the denominator reflect the different coupling schemes used in the calculation (\(M\)  = mesons, \(B\)  = baryon).
The modification of the \(\rho \)  meson via a dressing of the pion loops were calculated in [1]}, [2]},[3]}, [4]} within the framework of the \(\Delta \) -hole model and generally leads to the increase of the meson width.
The interactions with baryon resonances modify also the mass distribution and produce additional structures.
The interactions with higher mass baryon resonances were first considered for cold nuclear matter in [5]} and were limited to \(P\) -wave \(\rho -N\)  states.
Later, the calculations were extended to \(S\) -wave states [6]} thus elucidating the important role played by the low mass \(N^*\)  (\(D_{13}(1520)\) ) and \(\Delta ^*\)  (\(S_{31}(1620),S_{33}(1700)\) ) resonances.
In particular strong effects on the \(\rho \)  spectral function for small relative momentum of the vector meson w.r.t.  the medium (\(p \simeq 0\) ) were observed.
The momentum dependence of the \(\rho -N\)  coupling was further studied in [7]} by accounting also for relativistic effects.
The work confirmed the important role of S-wave resonances extended the study to the \(\omega \)  meson [8]}, [9]}, where a significant broadening of its spectral function, associated with appearance of low mass tail, was found.
The latter is due to strong off-shell coupling of the meson to S11(1535) resonance.
